Almost every country in the world has a railroad, one of our most important means of transportation. Laid end-to-end, the tracks of the world's railroads would stretch three times the distance from the earth to the moon (750,000 miles). Only ships carry heavier cargoes for longer distances. Only airplanes transport the public faster than railroads.
Although there were some "railroads" existing before 1804 they were either horse or man powered. The age of the modern railroad began with the invention of the steam engine. In 1804 a high-pressure steam engine was mounted on a four-wheeled vehicle designed to run along a track, and carried 9 metric tons (19,800 pounds), 5 wagons and 70 men. In 1830 the first passenger service was begun. The "iron horse" had arrived.
A steam engine is powered by making heat from burning coal or oil in a firebox. The heat turns the water in the boiler, into steam. The steam goes into cylinders that push against pistons. The pistons are connected to rods which move the wheels.
But, it takes a lot of time to light the fire and heat the boilers. It requires large amounts of coal to produce and maintain power, and most of the heat is wasted.
There are now less than 50 steam locomotives, most of them tourist attractions, still operating in the United States. Steam power has been replaced by either the diesel or the electric locomotive.
The diesel engine has several advantages. It uses less fuel, requires less servicing, and costs less to maintain. A diesel locomotive can make longer runs, as well as starting, stopping, and speeding up faster than the steam locomotive.
The diesel is an internal combustion engine. This means its power comes by burning an explosive mixture of gases. It is different than the usual car engine in that it does not use a spark plug to ignite the gases. As air is compressed it heats up in the cylinder, and eventually causes the gases to ignite. The power produced is transmitted to the driving wheels.
The diesel engine was invented in 1892, and the diesel locomotive was tried in 1923. In 1925 the first diesel passenger trains went into service. In 1940 the first freight diesels went into service. Today there are over 20,000 diesel locomotives operating in the United States.
Electric locomotives were introduced in the late 19th century. Electric locomotives do not generate their own power, like diesels do. They use power supplied by an electrical power plant that may be miles away. An electric locomotive, therefore, needs special wires or rails from which it can get power.
Many electric locomotives use a "third rail" which runs parallel to the regular rails on which the train travels. A metal device called a contact shoe is attached to the locomotive. The shoe slides along the third rail and picks up electricity from it.
Electric locomotives have several advantages over diesels:
Most track is made up of two steel rails running parallel and fastened to railroad ties (wooden beams in the roadbed). Each train wheel has a flange (rim) around its inner edge. The flanges on each pair of wheels guide the wheels along the track. Some track can be moved on pivots allowing the train to change from one track to another. These are called switches.
The roadbed on which tracks are laid is specially prepared to make the ride as level and smooth as possible, and to hold the ties in place and keep the track stable. The route of the track is planned to minimize (have less) steep grades and curves, which would reduce a train's speed and/or load.
In some cities the roadbed is above the ground (elevated) or under the ground (subway).
Before the automobile and the airplane most people traveled by train (and horse). Today, few people ride trains because the automobile is very easy to use and because the airplane is so much faster.
In China, India, Japan, and most of Europe the train is still heavily used for transportation. The problem with automobiles is the air pollution they cause. Road surface requirements, and gridlock (traffic jams) are other problems connected with cars.
New interest in special trains called "Monorails" may change the public opinion of trains for passenger transportation. Monorails ride on a single large rail which the train straddles. This makes the train ride quieter and smoother for the passengers.
Today, trains are developed using many of the same
principles used in aircraft and car
design. Engineers use the most modern methods to
reduce noise, improve safety, and
reduce drag. Streamlining the train or monorail
design generally reduces the fuel or
energy required to operate the vehicle.
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